The present invention generally relates to hydraulic dams, and, more particularly, to a moveable gate system including a wicket and downstream jack for use with a hydraulic dam. The moveable gate is mounted between two abutments which are constructed along river banks at the ends of moveable dam's floor or on the spillway crest of a gravity dam.
The following patents are known gate systems which consist of juxtaposed elements of small size which can be displaced independently of each other: U.S. Pat. No. 419,287 to Scaife; U.S. Pat. No. 2,335,327 to Wellons; U.S. Pat. No. 3,718,002 to Aubert; U.S. Pat. No. 3,775,983 to Aubert; U.S. Pat. No. 4,352,592 to Aubert; U.S. Pat. No. 5,178,490 to Snowberger; and French Patent 2,570,728 to Aubert. The gate elements generally take a nearly vertical end position, a substantially horizontal end position and a number of intermediate positions therebetween.
The gate elements include a wicket panel which is pivotally mounted on the floor or body of a dam and are held in one of the aforesaid positions by means of a prop supported on stop catches as disclosed in the Aubert patents and Snowberger '490, or by means of pins as disclosed in Scaife '287 and Wellons '327. In Snowberger '490, the downstream end of the prop includes a weak point which fails in the event that a floating object impacts the wicket.
In Aubert '002, '983 and '592, the moveable gate element comprises a tie-frame or horse which is pivotably mounted to the floor or body of the dam and a wicket panel. The wicket panel is pivoted about a horizontal shaft or hinge-pin attached to the horse. During normal operations, the wicket panel and the horse remain in contact. In the event of impact, the additional degree of freedom introduced by the interposition of the horse between the wicket panel and the dam floor is advantageous in retaining integrity of the dam.
In the following description, the term "wicket" refers not only to the wicket panel but also to the other movable components which are associated therewith. For example, "wicket" applies both to the wicket panel, which is pivotally mounted to a hinged horse, or to other juxtaposed and differently arranged elements having small dimensions.
In the Scaife, Aubert and Snowberger patents, the moveable gate system is provided with an operating device which comprises an oscillating jack rotatably mounted with respect to a horizontal shaft which is attached to the floor or body of the dam. An abutment member is included which is orientable about the horizontal shaft attached to the wicket, the abutment member being adapted to receive the extremity of the jack rod during wicket operation.
In U.S. Pat. Nos. 3,775,983, 4,352,592 and 5,178,490, the jack rod is immersed in oil by withdrawing into the interior of the jack body between two operations of the dam. Thus, the jack rod is protected from any adverse effects of being exposed to water except during the operation of the wicket which are of relatively short duration. Over exposure of the jack rod to water can result in oxidation or in erosion if the water contains suspended substances.
Aubert '983 further includes a device for locking the main Jack body in position between two operations. The locking device is controlled by supplying high pressure oil to the jack such that the locking action is suppressed automatically at the beginning of each operation by stopping the supply of oil. The system further comprises a device for locking the abutment member of the wicket dam between two operations.
Between two operations, the jack body on one hand and the abutment member of the wicket on the other hand accordingly retain the position which they assumed at the end of the previous operation. At the beginning of the next operation, the jack rod will be oriented towards the abutment member which will, in turn, be suitably positioned for receiving the jack rod.
In other known designs, various seals are provided to in the sill of the dam where the jack is partially housed and oscillating. This precludes the introduction of debris. Also, the removal of the sealing apparatus and the jack are facilitated by providing suitable seals. Examples of the above is French Patent No. 2,570,728 which discloses a sealing jacket in which the jack is partially encased and Snowberger '490 which discloses a slidable sealing means.
Snowberger includes an auxiliary alignment jack coupled to the lifting Jack for rotating the lifting jack between the corresponding position occupied by the wicket. A comparable design was also tested on a model stored at the Vives-Eaux dam on the Seine river near Paris.
In Aubert '592, the jack is associated with a restoring means which moves the jack to an angularly oriented end position, an extreme orientation, about its axis of pivotal motion when the jack operating rod is moved away from the abutment member. This end position is close to the positions assumed by the jack when the operating rod is in contact with the abutment member in the various inclined positions assumable by the wicket. The free end of the jack operating rod and the abutment member are provided with a guiding means. The guiding means ensures that the end of the jack operating rod is engaged with the abutment member when these components approach each other.
After each wicket operation, and as soon as the jack operating rod moves away from the abutment member and withdraws into the jack body, the restoring means places the jack in its extreme orientation. At the beginning of the following operation, the rod moves out of the jack body in the extreme orientation. When the end of the operating rod contacts the wicket's abutment member, the guiding means automatically brings the end of the operating rod into coincident relation with the abutment member.
The guiding means generally includes a cup fixed on the free end of the jack rod which is adapted to receive a spherical engaging member attached to the abutment member as taught by Aubert '592. In Snowberger '490, the guiding means comprises a separable cup bearing and a spherical wicket bearing mounted to a rear side of the wicket.
The prior art solutions to wicket dam construction involve a number of different problems. In Scaife '287, the jack is permanently connected either to the prop or to the wicket without posing an alignment problem. However, this arrangement is not convenient when the jack rod must be retracted within the jack body to protect it between two operations.
Aubert '002 also concerns a jack which is permanently connected to the wicket. Wellons '327 concerns a jack which is permanently aligned with the roller mounted on the wicket and is not amenable for use with oscillating cylinders.
Aubert '983 describes a sophisticated alignment means which is not sufficiently reliable. Aubert '592 describes a self alignment means in use on the Denouval dam which is difficult to employ in larger constructions. Snowberger '490 describes an alignment means which preferably uses an auxiliary Jack coupled to the lifting cylinder. This provides alignment to the single raised position of the wicket. Said model, tested at the Vives-Eaux dam and using an auxiliary jack system, did not provide a reliable locking of lifting cylinder.
French Patent No. 2,570,728 describes a sealing apparatus of the chamber provided in the sill in which the lower portion of the jack oscillates. The sealing apparatus includes a jacket which encases an upper portion of the jack and seals matching the contour of the jacket. Maintenance and repair of the jack and the sealing components is difficult due to the provision of the jacket and the seals.
It is desirable to provide an oscillating jack operated wicket dam which overcomes the aforementioned shortcomings of known designs and which provides improved chamber sealing in the sill of the dam to prevent the introduction of debris and silt.